Antioch police - triumphant after their swift capture of a man they suspect of snatching a 7-year-old girl at gunpoint outside her family home - are looking at other crimes the 43-year-old may have been involved in.

Police arrested David Allen Douglas on Friday night, about four hours after they say he kidnapped the victim, Natalie Calvo, and accosted her mother as they got out of their car in front of their home on the 3800 block of Hummingbird Drive in Antioch at 6:45 p.m.

Police believe the kidnapper followed the two home from their shopping trip to a Walmart store at 4893 Lone Tree Way.

"The mother attempted to stop the male from abducting her daughter and when she approached him, the male produced what's been described as a rifle, and the mom stopped," Antioch police Lt. John Vanderklugt said. "He was able to force the child into the car and then fled the scene."

The California Highway Patrol issued an Amber Alert, which was seen on highway signs and which interrupted evening television programs with news of the kidnapping.

Police found Douglas' tan 1996 Toyota Camry at the Antioch Marina about 11 p.m. Natalie was inside the car and safe, police said. An officer held Douglas at gunpoint until backup arrived, authorities said.

A day earlier, a man matching Douglas' description tried unsuccessfully to kidnap a young girl at the same Walmart, Vanderklugt said.

Police are also looking into another incident, also on Friday, in which Douglas was positively identified, police said.

Antioch Police Chief Allan Cantando spoke with pride about the work his officers did in rescuing Natalie.

"As I arrived at the police station I saw the men and women of this department, in conjunction with the FBI, diligently working leads, gathering information and coordinating this investigation," Cantando said in a statement. "Within a relatively short amount of time, investigators developed a suspect (David Douglas). Within the hour, Douglas was in custody and the brave 7-year-old girl was safe in police custody.

"As I stood in the foyer of the police department with a few of our amazing officers, I had the pleasure of telling the parents their daughter was safe and the suspect was in custody. It was an emotional moment for all of us."